What was found
(CAN) IN CRUISE PILOT REPORT RT ENGINE SURGING, THEN COMPLETELY ROUGH RUNNING. ENGINE SHUTDOWN, AIRCRAFT LANDED SAFELY. COMPRESSION TEST REVEALED ONE WEAK CYLINDER 50/80 PSI. BOTH SPARK PLUGS IN THAT CYLINDER SHORTED DUE TO BEING PEENED OVER BY FOREIGN OBJECT BOUNCING BACK AND FORTH IN CYLINDER. SUSPECT CERAMIC PIECE FROM A PLUG CAME OFF AND DID DAMAGE, HOWEVER PIECE NOT FOUND, NEW CYLINER ASSEMBLY INSTALLED, SPARK PLUGS ARE RECONDITIONED IN HOUSE USING CHAMPION PLUG CLEANER/TESTER.